Add support for generating presigned exit message from private key (#56)

* Add support for generating presigned exit message from private key

* Fix strings

README.md

@@ -108,6 +108,14 @@ Use `eth-staking-smith` via command line like:
 
 Note that --validator-beacon-index and --validator-seed-index are two distinct parameter, the former being index of validator on Beacon chain, and the latter is the index of validator private key derived from the seed
 
+It is also possible to directly pass private key with `--private-key` parameter instead,
+then `--mnemonic` and `--validator-seed-index` may be omitted like follows
+
+```
+./target/debug/eth-staking-smith presigned-exit-message --chain mainnet --private-key "0x3f3e0a69a6a66aeaec606a2ccb47c703afb2e8ae64f70a1650c03343b06e8f0c" --validator_beacon_index 100 --epoch 300000
+```
+
+
 
 ### Command to send VoluntaryExitMessage request to Beacon node
 

src/cli/presigned_exit_message.rs

@@ -13,8 +13,8 @@ pub struct PresignedExitMessageSubcommandOpts {
     /// argument, and wait for the CLI to ask you
     ///    for your mnemonic as otherwise it will
     ///    appear in your shell history.
-    #[arg(long)]
-    pub mnemonic: String,
+    #[arg(long, required_unless_present = "private_key")]
+    pub mnemonic: Option<String>,
 
     /// The name of Ethereum PoS chain you are targeting.
     ///
@@ -28,8 +28,16 @@ pub struct PresignedExitMessageSubcommandOpts {
     /// and you want to generate for the 2nd validator,
     /// the validator_start_index would be 1.
     /// If no index specified, it will be set to 0.
-    #[arg(long, visible_alias = "validator_seed_index")]
-    pub validator_seed_index: u32,
+    #[arg(
+        long,
+        visible_alias = "validator_seed_index",
+        required_unless_present = "private_key"
+    )]
+    pub validator_seed_index: Option<u32>,
+
+    /// Validator private key bytes in hex form
+    #[arg(long, required_unless_present_all = ["mnemonic", "validator_seed_index"])]
+    pub private_key: Option<String>,
 
     /// On-chain beacon index of the validator.
     #[arg(long, visible_alias = "validator_beacon_index")]
@@ -82,12 +90,24 @@ impl PresignedExitMessageSubcommandOpts {
             },
         );
 
-        let (voluntary_exit, key_material) = voluntary_exit::voluntary_exit_message_from_mnemonic(
-            self.mnemonic.as_bytes(),
-            self.validator_seed_index as u64,
-            self.validator_beacon_index as u64,
-            self.epoch,
-        );
+        let (voluntary_exit, key_material) = if self.mnemonic.is_some() {
+            voluntary_exit::voluntary_exit_message_from_mnemonic(
+                self.mnemonic.clone().unwrap().as_bytes(),
+                self.validator_seed_index.unwrap() as u64,
+                self.validator_beacon_index as u64,
+                self.epoch,
+            )
+        } else {
+            let secret_key_str = self.private_key.clone().unwrap();
+            let secret_key_bytes =
+                hex::decode(secret_key_str.strip_prefix("0x").unwrap_or(&secret_key_str))
+                    .expect("Invalid private key hex input");
+            voluntary_exit::voluntary_exit_message_from_secret_key(
+                secret_key_bytes.as_slice(),
+                self.validator_beacon_index as u64,
+                self.epoch,
+            )
+        };
 
         let signed_voluntary_exit =
             voluntary_exit.sign(&key_material.keypair.sk, genesis_validators_root, &spec);

src/key_material.rs

@@ -4,7 +4,7 @@ use eth2_keystore::{
     json_keystore::Kdf, keypair_from_secret, Keystore, KeystoreBuilder, PlainText,
 };
 use eth2_wallet::{KeyType, ValidatorPath};
-use types::Keypair;
+use types::{Keypair, SecretKey};
 
 use crate::utils::{pbkdf2, scrypt};
 
@@ -17,6 +17,22 @@ pub struct VotingKeyMaterial {
     pub withdrawal_keypair: Option<Keypair>,
 }
 
+impl VotingKeyMaterial {
+    pub fn from_voting_secret_bytes(voting_secret_bytes: &[u8]) -> Self {
+        let sk = SecretKey::deserialize(voting_secret_bytes).expect("Invalid private key passed");
+        let pk = sk.public_key();
+        let keypair = Keypair::from_components(pk, sk);
+        let voting_secret = voting_secret_bytes.to_vec().into();
+
+        Self {
+            keypair,
+            voting_secret,
+            keystore: None,
+            withdrawal_keypair: None,
+        }
+    }
+}
+
 /// Key derivation function for the keystore
 #[derive(clap::ValueEnum, Clone)]
 pub enum KdfVariant {

src/voluntary_exit/mod.rs

@@ -33,5 +33,20 @@ pub fn voluntary_exit_message_from_mnemonic(
     (voluntary_exit, key_material.clone())
 }
 
+pub fn voluntary_exit_message_from_secret_key(
+    secret_key_bytes: &[u8],
+    validator_beacon_index: u64,
+    epoch: u64,
+) -> (VoluntaryExit, VotingKeyMaterial) {
+    let key_material = VotingKeyMaterial::from_voting_secret_bytes(secret_key_bytes);
+
+    let voluntary_exit = VoluntaryExit {
+        epoch: Epoch::from(epoch),
+        validator_index: validator_beacon_index,
+    };
+
+    (voluntary_exit, key_material)
+}
+
 #[cfg(test)]
 mod test;

tests/e2e/presigned_exit_message.rs

@@ -149,3 +149,37 @@ fn test_presigned_exit_message_send_beacon_node() -> Result<(), Box<dyn std::err
 
     Ok(())
 }
+
+#[test]
+fn test_presigned_exit_message_private_key() -> Result<(), Box<dyn std::error::Error>> {
+    let chain = "mainnet";
+    let private_key = "0x6d446ca271eb229044b9039354ecdfa6244d1a11615ec1a46fc82a800367de5d";
+    let validator_index = "100";
+    let epoch = "305658";
+
+    // run eth-staking-smith
+    let mut cmd = Command::cargo_bin("eth-staking-smith")?;
+
+    cmd.arg("presigned-exit-message");
+    cmd.arg("--chain");
+    cmd.arg(chain);
+    cmd.arg("--validator_beacon_index");
+    cmd.arg(validator_index);
+    cmd.arg("--private-key");
+    cmd.arg(private_key);
+    cmd.arg("--epoch");
+    cmd.arg(epoch);
+
+    cmd.assert().success();
+
+    let output = &cmd.output()?.stdout;
+    let command_output = std::str::from_utf8(output)?;
+
+    let signed_voluntary_exit: SignedVoluntaryExit = serde_json::from_str(command_output)?;
+    assert_eq!(
+        signed_voluntary_exit.signature.to_string(),
+        "0xa74f22d26da9934c2a9c783799fb9e7bef49b3d7c3759a0683b52ee5d71516c0ecdbcc47703f11959c5e701a6c47194410bed800217bd4dd0dab1e0587b14551771accd04ff1c78302f9605f44c3894976c5b3537b70cb7ac9dcb5398dc22079"
+    );
+
+    Ok(())
+}